void setup() {
  size(600,600);
  background(220);
  smooth();
  noStroke();
}  
void draw() {
  background(220);
  int s = second();
  float ang = map(s, 0, 60, -HALF_PI,3*HALF_PI);
  arc(width/2, height/2, width, height,
       -HALF_PI, ang);   
}


